1. Field of the Invention
Aspects of the present invention relate to a binder for an electrode of fuel cells. More particularly, aspects of the present invention relate to a binder for an electrode of fuel cells that improves proton conductivity by minimizing structural changes of the electrode, improving phosphoric acid retention capacity, and increasing wetting velocity of a catalyst layer. Aspects of the present invention further relate to an electrode for fuel cells including the binder, a method of manufacturing the electrode, and a fuel cell using the electrode.
2. Description of the Related Art
Proton conductors that have excellent and stable proton conductivity at a temperature in the range of 100-300° C. over a long period of time are required in fuel cells in order to provide power generation efficiency, system efficiency, and long-term durability of elements constituting the fuel cells.
In solid polymer electrolyte membrane fuel cells (PEMFCs), which use phosphoric acid as a proton conductor, a sufficient amount of phosphoric acid, as a proton conducting medium, needs to be supplied for electrochemical reactions and high proton conductivity in electrodes. The impregnation degree and distribution of the phosphoric acid in the catalyst layer are important factors affecting cell performance in fuel cells.
Polyvinylidene fluoride (PVDF) and polybenzimidazole (PBI), which are stable in phosphoric acid as electrolytes of a Pt/C catalyst, have been widely used as binders for electrodes of fuel cells. (Japanese Patent Publication No. 2006-019271).
However, when PVDF is used as a binder, the phosphoric acid may not be sufficiently distributed, and fluidity may not be fully controlled. When PBI is used as the binder, the electrode may be partially damaged due to the solubility of PBI in phosphoric acid, and micro-structural changes may occur in the electrode due to swelling of the electrode.